METHOD FOR REVAMPING AND INCREASING THE CAPACITY OF A HYDROCARBON REFORMING SECTION

Abstract

A method for revamping a reforming section of a chemical plant, wherein the reforming section treats a first hydrocarbon feed stream, and an apparatus downstream of the reforming section, designed as a steam generator, is converted into a GHR by means of the following steps: replacing the heat exchange bodies of said steam generator with heat exchange bodies containing a reforming catalyst; directing a second hydrocarbon feed stream inside said heat exchange bodies containing catalyst; extracting a reformed gas stream from said heat exchange bodies.

Claims

1-8. (canceled)

9. A method for revamping a reforming section of a chemical plant in which: the reforming section receives a first stream of a hydrocarbon feed and steam and converts the first stream into at least partially reformed gas; the chemical plant includes at least one apparatus operated as heater or evaporator of a fluid and comprising a shell and first heat exchange bodies, wherein the at least one apparatus is heated with at least partially reformed hot gas coming from the reforming section and fed to the shell side, and the fluid is heated and/or evaporated inside the first heat exchange bodies by means of indirect heat exchange with the hot gas; the method comprising: modifying the at least one apparatus by replacing the first heat exchange bodies with second heat exchange bodies containing a reforming catalyst; providing a hydrocarbon feed line arranged to direct a second stream of a hydrocarbon feed inside the second heat exchange bodies; and providing a line arranged to withdraw an at least partially reformed gas stream from the second heat exchange bodies; the at least one apparatus thus being converted into a gas heated reformer.

10. The method of claim 9, wherein the second heat exchange bodies have an outlet that is in communication with the shell side of the at least one apparatus, so that the at least partially reformed gas produced in the first heat exchange bodies is mixed with the at least partially reformed gas supplied from the reforming section, forming a stream of gaseous product which is withdrawn from the shell of the at least one apparatus.

11. The method of claim 9, wherein the first and second heat exchange bodies include tubes belonging to a first and a second tube bundle respectively, and the method comprises: extracting the first tube bundle from the shell of the at least one apparatus; and inserting the second tube bundle into the shell.

12. The method of claim 11, wherein the first tube bundle and the second tube bundle comprise a single flange, so that the first tube bundle and the second tube bundle can be respectively extracted and inserted from one side only of the at least one apparatus.

13. The method of claim 9, wherein the at least one apparatus is vertical.

14. The method of claim 9, wherein the at least one apparatus, converted into a gas heated reformer, operates in parallel with the existing reforming section, wherein a part of a hydrocarbon feed is directed to the existing reforming section and another part of the hydrocarbon feed is directed to the at least one apparatus converted into a gas heated reformer.

15. The method of claim 9, wherein two steam generators downstream of the reforming section are converted respectively into a first and a second gas heated reformer, respectively.

16. The method of claim 9, wherein the chemical plant is a plant for methanol synthesis or for ammonia synthesis.

Description

DESCRIPTION OF THE FIGURES

[0042] FIG. 1 shows a scheme of a reforming section with a steam generator.

[0043] FIG. 2 shows the section shown in FIG. 1 modified in accordance with the invention, converting the steam generator into a GHR.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0044] FIG. 1 is a simplified diagram of a reforming section according to the prior art, which may be found for example in an ammonia or methanol plant.

[0045] A charge 1 containing steam an at least one hydrocarbon, for example natural gas, is converted in a reforming section 2 to produce a high-temperature reformed gas 3.

[0046] The section 2 is fed with a fuel F directed, for example, to the burners of a primary reformer.

[0047] Before further treatment and conversion into the product concerned, the reformed gas 3 flows into the shell side of a vertical tube boiler 4, or waste heat boiler (WHB).

[0048] Said boiler 4 is a shell-and-tube apparatus.

[0049] In greater detail, the boiler 4 contains a tube bundle 5 inside a shell 6. The tube bundle 5 comprises a plurality of bayonet tubes 17 and a single tube plate 10. Each bayonet tube 17 is formed by an outgoing tube and by a return tube coaxial with the outgoing tube, such that the inlet and outlet of the tube bundle are located on a same side, and the tube bundle is supported by a single tube plate 10 according to a known embodiment which comprises means (not shown) for separating the incoming flow from the outgoing flow.

[0050] This design with bayonet tubes and single plate allows easy extraction of the tube bundle from the shell. In fact, it is possible to open the shell 6, by unscrewing the bolts of the flange 10, and extract the tube bundle 5, i.e. the tube assembly 17 and the associated plate 10 and cover 16.

[0051] The tube bundle 5 is fed with water 7 and produces a stream 8 containing steam and water. The cooled gas 9, output from the shell side, is conveyed to appropriate further process stages, for example for purification and conversion.

[0052] FIG. 2 shows the modified reforming section according to the invention. The apparatus 4 is modified by extracting the tube bundle 5 from the shell 6 and inserting a new tube bundle 11 into the shell 6. Said new tube bundle 11 comprises a plate 18 and tubes 12 containing a reforming catalyst (for example the same catalyst used in the reforming section 2).

[0053] An additional hydrocarbon feed stream 1a is directed into the tubes 12. Said flow 1a may form part of a hydrocarbon source which also supplies the stream 1 to the section 2.

[0054] Advantageously, owing to the addition of the stream 1a, the total quantity of hydrocarbon which can be reformed in FIG. 2 is greater than the quantity which can be reformed in FIG. 1, i.e. the reforming capacity is increased. In other words the modified reforming section, according to the invention, is able to process the stream 1a in addition to the stream 1 and consequently has an increased capacity.

[0055] The apparatus 4, originally intended to act as a steam generator, is thus converted into a GHR 40. It should be noted that the original shell 6 is maintained, with significant cost savings compared to the installation of a new GHR.

[0056] In greater detail, each of the tubes 12 has an inlet end 13 for said stream 1a and an opposite outlet end 14 for reformed gas, which communicates with the shell side of the apparatus 40. Consequently, the reformed gas produced inside the tubes 12 is mixed with the incoming hot gas 3 and may be extracted from the apparatus 40 via the reformed gas outlet 9 on the shell side.

[0057] The incoming gas 3 (from the reforming section 2) is preferably distributed in the shell side via a distributor 15 with holes, enters the bottom part of the shell 6, where it is mixed with the gas output from the tubes 12, and flows upwards along the tube bundle 11, releasing the heat necessary for the reforming steam reaction, and leaves at the top of the shell 6 through the outlet 9.

[0058] The reformed gas 9 leaving the GHR 40 has a temperature which is still relatively high and, if necessary, can be used for steam production before the necessary process treatments.

[0059] The new tube bundle 11 can be bolted to the same pre-existing flanges 10 and the operation of replacing the bundle 11 with the reforming bundle 12 is relatively simple.

[0060] In some embodiments the plant comprises a plurality of steam generators, for example two steam generators, downstream of the reforming section, which can be modified as described above. For example a typical arrangement comprises two vertical boilers downstream of a secondary reformer and both said vertical boilers are converted into GHRs as described above.